Flooded lead acid batteries (batteries with liquid electrolyte) designed for starting, lighting and ignition (SLI) experience a variety of rough handling during manufacture, storage and distribution including an occasional accidental tilting of the battery on its side, a variety of angled inclines once the battery is installed within a vehicle, as well as normal vibrations. During normal operation of a battery, water is electrolyzed into hydrogen and oxygen while temperature excursions produce water vapor, both of which will tend to be lost through the battery venting system. A well designed vent network must minimize or prevent this loss by capturing, condensing and draining the acid back into the cells. The vent system must also prevent or minimize spilling even when the battery is inverted, and safeguard the battery against external ignition sources. Typically, the vent system is incorporated into individual cell closures or, in the more modem battery designs, in vent manifold covers which extend over several or all of the cell openings. The vent system usually includes an electrolyte flowpath arrangement in combination with one or more vent recesses or ports in which flame arresters are seated. These flame arresters are usually in the form of glass or polypropylene "frits" which permit the passage of vapor out of the battery casing but prevent flame intrusion into the battery. At the same time, the electrolyte flowpath is designed to minimize spilling, at least when the battery is tilted 90.degree. to one side or the other. See, for example, commonly owned U.S. Pat. No. 5,565,282.
Tougher criteria are currently being implemented, or will be implemented in the future, regarding spillage of electrolyte from flooded lead acid batteries to the extent of requiring spillage prevention even when the battery is turned over, i.e., inverted. Thus, there is a need to have flooded lead acid batteries designed to prevent the spilling of corrosive acids not only when the batteries are subjected to a high degree of tilt or even turned on one side, but also when the battery is turned completely upside down as may happen in an automobile accident or as a result of accidental mishandling during installation, removal or transit. Presently, this goal is accomplished by an expensive lead acid battery design utilizing gelled electrolytes, or by using AGM oxygen recombinant valve regulated (VRLA) batteries.
In accordance with this invention, the battery vent cover or manifold cover is designed to cooperate with a complementary or mating surface configurations on the battery casing lid to establish an electrolyte flowpath which substantially confines the liquid electrolyte to specific areas adjacent the cell opening, and which prevents lateral spillage into adjacent cells in all battery orientations with the exception of a complete inversion. Thus, the flowpath arrangement in accordance with the invention is effective for battery tilt orientations 90.degree. in any direction, i.e., where the battery rests on any of its four peripheral sides. Spillage of the electrolyte out of the battery casing when the battery is inverted can be prevented by the use of a specially designed PTFE frit as described and claimed in commonly owned co-pending application Ser. No. 09/042,720, filed on Mar. 17, 1998, the entirety of which is incorporated herein by reference. While these two design features can be incorporated individually or in combination, the greatest benefit is achieved when they are combined in a single battery.
In one exemplary embodiment, a manifold vent cover is provided which is formed on its underside with ribs and walls which, in use, are heat sealed to mating, complementary ribs and walls on the upper surface of the battery casing cover or lid, and which together define substantially closed electrolyte flow paths for each cell. Since the flowpath for each cell is substantially identical, the description of one is sufficient. Part of the flowpath for each cell is defined by a hollow, cylindrical "chimney" formed in the battery casing cover and which extends below the underside thereof. In the area below the cover, the chimney is provided with vertically offset 180.degree. ramps or baffles, in diametrically opposed relationship. The ramps are in fact, conical surfaces with central openings, i.e., each has a half circle cutout concentric with the longitudinal axis of the chimney. These ramps serve as splash guards and also facilitate drainage of splashed or spilled electrolyte back into the cell. The cooperative interfit of the splash tubes within the staggered ramps obviates the need for special "guides" inside the manifold cover which are notorious acid collectors and tend to accumulate beads of acid which will eventually find their way out of the cover.
At the same time, the underside of the manifold cover is formed with a plurality of downwardly extending splash guard tubes which are sized and located to extend into the chimneys on the battery cover. These tubes are open at their lower ends and closed by the manifold cover at their upper ends. The tube radius approximates the radius of the opening in the upper ramp so that, when the manifold cover is sealed to the battery cover, the tips of the tubes lie concentrically within the upper ramp. Thus, to escape the battery cover, any electrolyte from a given cell must follow a somewhat circuitous path around the lower ramp, upper ramp, and then upwardly around the splash tubes. In addition, the very nature of the double ramp arrangement provides splash protection by deflecting the electrolyte back into the cell.
On the upper side of the battery casing cover, vertical walls define a rectangular chamber around each chimney, each chamber having a pair of side walls and a pair of end walls. The chimney extends above the battery cover surface to the same extent as the chamber peripheral walls, and is open at the top. In addition, a circumferential gap is formed in the chimney wall so that, when the manifold cover is sealed to the battery cover, the vertically oriented. circumferential gap is the only opening by which electrolyte can escape the chimney and pass into the rectangular chamber between the battery casing lid and the manifold cover.
Within the rectangular chamber, there is also a wall tangential to the chimney, which extends to one of the chamber sidewalls. This tangential wall is substantially adjacent the circumferential gap in the chimney, and extends parallel to the chamber end walls, lying on the opposite side of the chimney from the nearest one of the end walls. As a result, any electrolyte passing through the circumferential gap must then pass around the outside of the chimney, approximately 180.degree., to enter the main area of the rectangular chamber.
It will be appreciated that the manifold cover has complementary or mating ribs so that the chamber for each cell is closed (including the upper end of the respective chimney), except as noted below, when the manifold cover is sealed to the battery casing cover.
The ribs on the underside of the manifold cover which define part of the sidewalls of the chamber each have a notch located between the end walls, permitting vapor to escape from any one or more of the cells to the vent ports at opposite ends of the manifold cover. Thus, under normal circumstances, vapor within the cells can escape by following a flowpath up through the chimneys and through the individual chambers in the manifold cover by means of the notches in the chamber sidewalls, and then passing through the vent ports containing the flame arrester frits. Should any splashing of electrolyte occur during use, the chimney and splash tube arrangement in conjunction with the chamber arrangement within the manifold cover will confine the electrolyte to the individual cells and will facilitate quick drainage of electrolyte back into the battery. In this connection, the "floor" of the chamber in the manifold cover is tilted back toward the cell opening.
As further described in detail hereinbelow, the flowpath arrangement will also confine the electrolyte within the individual cell chamber areas in the event the battery is tilted over onto any one of its four sides. In this regard, the vapor passage notches in the chamber side walls are located at strategic positions in the chamber side walls such that it is not likely that any electrolyte will reach those notches and pass between the adjacent chambers when the battery is tilted over. As already noted above, in order to insure complete spillage protection even if the battery is completely inverted, PTFE frits of the type disclosed in the '720 copending application can be utilized in combination with the novel electrolyte flowpath design as described hereinabove.
Accordingly, in its broader aspects, the present invention relates to a battery configuration including a casing having bottom, side and top surfaces, the top surface having a plurality of cell openings therein, an improved flowpath for liquid electrolyte when the battery is tilted onto any one of its side surfaces, the flowpath comprising a cover chamber for each cell opening defined by a substantially rectangular peripheral wall surrounding the cell opening; a cylindrical wall surrounding and substantially concentric with the cell opening and located within the substantially rectangular wall, the cylindrical wall interrupted by a relatively small circumferential gap; a wall extending between the cylindrical wall and an adjacent side of the peripheral wall, the wall tangential to the cylindrical wall and adjacent the gap.
Other objects and advantages of the present invention will become apparent from the detailed description which follows.